Grey water footprint of a dairy industry wastewater treatment plant: a comparative study

Available fresh water demand of a growing population is a fundamental concern of water resource sustainability. Dairy industry wastewater treatment plants have been considered a major polluter due to the high organic content and large wastewater discharges. Grey water footprint (GWF) was developed by the Water Footprint Network (WFN) as a measure of the water pollution loading. In this study, four treatment scenarios including no treatment process (Scenario-1), primary treatment using Dissolved Air Flotation (DAF) (Scenario-2), secondary treatment using DAF and a Upflow Sludge Bed (UASB) reactor (Scenario-3), and a DAF and UASB with a reuse application applying reverse osmosis (RO) (Scenario-4) have been studied for a full-scale dairy industry wastewater treatment plant. For these four scenarios, GWF assessment was undertaken using the WFN method by taking into consideration three pollutant parameters, chemical oxygen demand (COD), fats, oil and grease (FOG) and total suspended solids (TSS). The results show that the GWF of Scenario-4 for COD was lowest with the value of 5,609 m/d and Scenario-1 has the highest GWF for TSS with the value of 41,026 m/d. According to the assessment results, reuse applications decrease the GWF values.